1. Field
The present disclosure relates to a control apparatus for a cooling system which is used in air-conditioning equipment, or the like, and which circulates cooling water between a cooling tower and a refrigeration device.
2. Related Art
In general, a cooling system which is used in air-conditioning equipment, and the like, is provided with a cooling tower, a refrigeration device, and an air conditioner which is the cooling load, and cooling water that has been cooled in the cooling tower is sent to the refrigeration device by a cooling water pump, and in the refrigeration device, heat exchange is performed with cold water which cools the air conditioner. Japanese Patent Application Publication No. 2000-283527, for example, describes a control apparatus for a cooling system of this kind.
In this cooling system, the cold water produced by the refrigeration device is supplied to the air conditioner by a cold water pump and is returned to the refrigeration device after receiving heat exchange processing in the air conditioner. On the other hand, in the cooling tower, a cooling fan for cooling the cooling water by blowing air is provided, and the cooling water cooled in the cooling tower is sent to the refrigeration device by the cooling water pump, and is returned to the cooling tower after performing heat exchange in the refrigeration device. Either both or one of an inlet temperature sensor, which detects the cooling water temperature at an inlet of the cooling tower, and an outlet temperature sensor, which detects the cooling tower temperature at an outlet of the cooling tower, are provided in pipes of the cooling water.
The possible control methods for a cooling system of this kind include: “control of the cooling fan”, “control of the cooling water pump” and “control of both the cooling fan and the cooling water pump”, and the like, and in these methods the number of revolutions of the cooling fan and/or the cooling water pump is controlled, thereby adjusting the flow volume of cooling air and the flow volume of cooling water, by adjusting the output frequency of an inverter apparatus on the basis of the detection values for the inlet temperature and the outlet temperature of the cooling water.
Below, “control of the cooling fan” is described, but the same applies to “control of the cooling water pump” and “control of both the cooling fan and the cooling water pump”, and in each of these cases, control is implemented on the basis of uniform inlet temperature control for controlling the cooling water temperature at the cooling tower inlet to a uniform temperature, or uniform outlet temperature control for controlling the cooling water temperature at the cooling tower outlet to a uniform temperature, or uniform temperature differential control for controlling the temperature differential between the inlet temperature and the outlet temperature of the cooling water at the cooling tower to a uniform differential.
Uniform inlet temperature control by control of the cooling fan involves detecting the cooling water inlet temperature at the inlet of the cooling tower, and controlling the number of revolutions of the fan motor which drives the cooling fan, by the inverter apparatus, in such a manner that the detected value of the cooling water inlet temperature matches a previously established inlet temperature set value.
With this uniform inlet temperature control, when the cooling water inlet temperature is low, it is not necessary to cool the cooling water greatly in the cooling tower, and therefore the output frequency of the inverter apparatus is lowered to reduce the number of revolutions of the fan motor, whereas when the cooling water inlet temperature is high, it is necessary to cool the cooling water in the cooling tower, and therefore the output frequency of the inverter apparatus is raised to increase the number of revolutions of the fan motor.
Furthermore, uniform outlet temperature control by control of the cooling fan involves detecting the cooling water outlet temperature at the outlet of the cooling tower, and controlling the number of revolutions of the fan motor which drives the cooling fan, by the inverter apparatus, in such a manner that the detection value of the cooling water outlet temperature matches a previously established outlet temperature set value.
With this uniform outlet temperature control, when the cooling water outlet temperature is low, it is not necessary to cool the cooling water greatly in the cooling tower, and therefore the output frequency of the inverter apparatus is lowered to reduce the number of revolutions of the fan motor, whereas when the cooling water outlet temperature is high, it is necessary to cool the cooling water in the cooling tower, and therefore the output frequency of the inverter apparatus is raised to increase the number of revolutions of the fan motor.
Moreover, uniform temperature differential control by control of the cooling fan involves determining the temperature differential between the cooling water inlet temperature and the cooling water outlet temperature, from the detection values for the cooling water inlet temperature at the cooling tower inlet and the cooling water outlet temperature at the cooling tower outlet, and controlling the number of revolutions of the fan motor which drives the cooling fan, by the inverter apparatus, in such a manner that the temperature differential is uniform.
With this uniform temperature differential control, when the temperature differential of the cooling water between the inlet and the outlet is small, it is not necessary to cool the cooling water greatly in the cooling tower, and therefore the output frequency of the inverter apparatus is lowered to reduce the number of revolutions of the fan motor, whereas when the temperature differential is large, conversely, it is necessary to cool the cooling water in the cooling tower, and therefore the output frequency of the inverter apparatus is raised to increase the number of revolutions of the fan motor.